ATLAS (Astrophysics Telescope for Large Area Spectroscopy) Probe is a concept for a NASA probe-class space mission, the spectroscopic follow-up to WFIRST, multiplexing its scientific return by obtaining deep slit spectroscopy with R=1000 over the wavelength range of 1-4 microns for ~200M galaxies imaged by WFIRST out to z = 7 in three tied surveys (Deep, Medium, and Wide), and deliver spectra that enable a wide range of diagnostic studies of the physical properties of galaxies over most of cosmic history. ATLAS Wide Survey will measure spectroscopic redshifts for ~70% of the galaxies over 2000 sq deg imaged by WFIRST High Latitude Survey at z > 0.5, removing the systematic bias due to photometric redshifts in cosmological constraints from weak lensing. ATLAS and WFIRST together will produce a 3D map of the Universe with sub-Mpc resolution in redshift space (sufficient for tracing the filaments in the cosmic web).
ATLAS science spans four broad areas:
- Revolutionize galaxy evolution studies by tracing the relation between galaxies and dark matter from galaxy groups to cosmic voids and filaments, from the epoch of reionization through the peak era of galaxy assembly;
- Open a new window into the dark Universe by obtaining definitive measurements of dark energy and modification of General Relativity using galaxy clustering, and weighing the dark matter filaments using 3D weak lensing with spectroscopic redshifts;
- Probe the Milky Way's dust-enshrouded regions, reaching the far side of our Galaxy; and
- Explore the formation history of the outer Solar System by characterizing Kuiper Belt Objects.
ATLAS is a 1.5m telescope with a field of view (FoV) of 0.4 sq deg, and uses Digital Micro-mirror Devices (DMDs) as slit selectors. It has a spectroscopic resolution of R = 1000, a wavelength range of 1-4 microns, and a spectroscopic multiplex factor greater than 5,000. ATLAS will orbit around the Sun-Earth L2 Lagrange point. It will have a 5 year prime mission that includes Guest Observing time. ATLAS is designed to fit within the NASA probe-class mission cost envelope; it has a single instrument, a telescope aperture that allows for a lighter launch vehicle, and mature technology (DMDs can reach TRL 6 within 2 years). ATLAS will lead to transformative science over the entire range of astrophysics.
For an introduction to ATLAS Probe, see the invited ATLAS Probe presentation to Astro2020 (click on "Atlas Probe presentation" at https://www.nationalacademies.org/event/03-17-2020/astro2020-panel-on-electromagnetic-observations-from-space-1-meeting-3
Send questions or comments to Yun Wang (wang at ipac.caltech.edu).